1. Field of the Invention
This invention relates generally to a personal locator beacon (PLB) that is used to transmit an emergency distress signal, and particularly to a PLB that transmits an emergency distress signal containing security information warning the emergency response team of danger.
2. Description of Related Art
Through advances in electronics combined with the existing satellite infrastructure, global positioning systems (GPS) technology provides a means of locating anyone or anything on Earth. GPS has become extremely widespread, particularly in automobiles through the use of GPS navigation systems. Moreover, improvements in electronics have enabled the development of small and portable devices that when integrated with a GPS, can operate as emergency beacons. These personal locator devices are used extensively in rescue situations when an individual is in danger.
An entire organization COSPAS-SARSAT (The International Satellite-Based Search and Rescue Distress Alert Detection and Information Distribution System) exists as an infrastructure to receive and respond to emergency distress signals. Specifically, a typical locator device emits a radio frequency (RF) distress signal. Within this distress signal, GPS information is usually included to specify the exact global position of the distress signal source. The COSPAS-SARSAT system includes not only a network of satellites, but also a reticulation of land based satellite dishes, satellite control centers and emergency response organizations. Through this land based system provided for by COSPAS-SARSAT, distress signals received by satellites, are transmitted down to a local user terminal (LUT). The LUT then sends the signal to the proper search and rescue authorities, who perform the appropriate response to the distress message.
The prior art teaches a variety of PLBs to activate and transmit emergency messages. Specifically, U.S. Pat. No. 6,285,281 issued to Gatto, discloses an emergency messaging transmitter that combines a GPS receiver with a marine antenna to transmit both a distress message and a voice message to the appropriate emergency response crew. The device, however, is limited to maritime applications as it must be coupled to a marine radio with a microphone.
U.S. Pat. No. 5,043,736 issued to Darnell et al., describes a personal locator device and system that also utilizes GPS technology and any means of communicating with a central station to convey an emergency distress message. The device also utilizes a panic button to spend special emergency signals to the central monitoring station. The emergency message can be transmitted through a PSTN/Cellular connection. One disadvantage is that the described system does not work within the COSPAS-SARSAT system, thus requiring the creation of a large infrastructure to support the needs of the subscribers to the service.
U.S. Pat. No. 6,014,080 issued to Layson, Jr., discloses an emergency beacon that is small and portable, making it easily concealable. Upon activation of the device, an infrared signal representing an emergency signal is transmitted. The device can be activated by either the wearer of the unit, or a respondent in a central station. The infrared signal is detected by a searching authority and located using a device located within a second vehicle. The disadvantage of this invention is that it also is not implemented in to the COSPAS-SARSAT system. Also, instead of utilizing a GPS system, at least two respondents are necessary for locating the infrared source beacon.
A wide array of potential applications exists for emergency beacon technology. These applications include EPIRBs (Emergency Position-Indicating Radio Beacons), which are used to signal maritime disasters and ELTs (Emergency Locator Transmitters), which are used to signal aviation disasters. Furthermore, PLB (Personal Locator Beacons) can also be used by any individual undertaking a dangerous task with the potential for becoming lost, such as mountain climbing, or backcounty skiing. In one of the more promising fields, emergency beacon technology is already used extensively throughout the military. One problem that has not been addressed by the prior art, is an effective means of transmitting security messages that warn of danger, within the distress signals that are sent through the COSPAS-SARSAT system. Specifically, when a person has become kidnapped and held hostage or when there is a danger of ambush, it is critical that the search and rescue team be warned without alerting the captures that a warning signal is being transmitted with the emergency signal.